Pruning and Feeding Hydrangeas: Timing, Soil pH, and Bloom Color

Pruning Hydrangeas: When and How

Hydrangeas bloom on old wood, meaning the flower buds for next summer form on the growth produced this year. Pruning in spring—often done as part of spring cleaning—removes those buds and results in fewer or no blooms. The best practice is to prune in early autumn, right after flowering finishes. If you prune in March, you are cutting off the very wood that would have produced flowers.

Regarding the tip about cutting back to a pair of leaf buds to double flowers: that technique encourages more branching, which can lead to more but smaller flower heads. If you prefer fewer, larger blooms, avoid heavy pruning and simply remove dead or weak stems.

Soil pH, Lime, and Aluminum Sulfate

Liming a lawn raises soil pH very slowly—typically no more than one pH unit, and even that takes a long time. The lime applied by your lawn company is likely counteracting the acidity from nitrogen fertilizers, not dramatically changing the soil chemistry around your hydrangeas.

The popular belief that soil pH alone controls hydrangea color (acid = blue, alkaline = pink) is largely a myth. Hydrangea color is primarily determined by genetics. While aluminum sulfate can enhance blue tones in some varieties by making aluminum available in acidic soil, the effect is modest and requires consistent, long-term application. It is not a quick fix, and results vary widely.

Encouraging Larger Flowers

For larger blooms next year, focus on proper pruning (autumn only), full sun exposure (or as much as possible), and avoiding high-nitrogen fertilizers that promote foliage at the expense of flowers. If a stem has multiple buds, you can remove all but the single strongest bud to direct energy into one large flower head.